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Old 16th June 2019, 17:50   #1
mbonwick
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Default What am I missing?? Help needed!

I've been away for a week, which has given me a chance to clear my mind of the 75 nightmare, now I'm back with no better ideas and looking for some help...
Engine is a 1.8 non-turbo running on 135 cams, with the head port-matched to a metal VVC manifold. ECU map has been changed to one based on the MG 135 map by CivilSteve.

Cold start - catches easy enough, but feels like it's only on 3.5 cylinders, takes maybe 5 sec to smooth out (but still not great), then from there the idle quality just falls apart until it's running on 2 cylinders before stalling itself. Smells very rich, needs throttle to keep it running.

Hot start - no more difficult to start, but idle is very rough until idle control kicks in after 30ish seconds, and the fuel trim is leaned out by the ECU (I've watched it on pscan live data). Again, smells rich even though the fuel trim is at maximum leaning (data shows 75%).

General driving - it's a complete nightmare when cold, very down on power. Less so when hot though. No MIL light, or any helpful error codes (P0300 - multiple misfire, P1316 - misfire causing excess emissions and P0170 - fuel trim malfunction are the only codes)


My first thought was a head gasket issue, as I had to revert to an elastomer gasket from the MLS due to flush liner induced failure. However there's no mayo or residual coolant pressure to indicate an issue.
Cylinder compressions are 180-160-160-200 psi. A bit uneven, but then the valves have been unshrouded so this may explain it.
Regardless, a cylinder leakdown test was fine, no leaking of compression.
No manifold leaks or anything else obvious to explain this, and neither of the 2 garages it has been in to have any further ideas.

At the suggestion of the second garage I've replaced the IACV as it's movement was a bit sticky (confirmed by me when I got the car back), and have ordered a fuel pressure regulator (but honestly I don't see this being the issue).




So, what have I missed here? What do I do now?
I really need to start making meaningful progress as the MOT is up at the end of July, it won't pass the emissions as it stands and it's my daily driver.
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Old 16th June 2019, 18:12   #2
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Have you tried something simple like reducing the plug gap to .75mm
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Old 16th June 2019, 18:25   #3
mbonwick
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Quote:
Originally Posted by suzublu View Post
Have you tried something simple like reducing the plug gap to .75mm

Well that's what I've missed....from my post!

Plug gap is already at .75mm
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Old 16th June 2019, 19:23   #4
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Could be, but I would expect that to get worse with higher revs, not better.

Coil packs are only 2 years old, and the charging times reported in livedata look reasonable (2700 and 3000 us respectively).
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Old 16th June 2019, 19:26   #5
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Id revert to the standard map and see if anything changes.
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Old 16th June 2019, 20:20   #6
mbonwick
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I'm contemplating that as my next step, however again I don't think it's the map that's the issue.
Reason being that it's had an issue with an overly rich cold idle (and subsequent rough running) ever since I did the head swap, and before the mapping was done. The mapping made no difference at the time, and it's only the CHG swap that's made things worse since.


I am leaning towards it being an ECU related issue though, is it worth (if I can find a competent T4 operator relatively near) having the idle reset and the adaptions erased? What does the T4 idle adjustment actually do?
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